Kickdown unit for an automotive automatic power transmission

ABSTRACT

A kickdown unit for effecting a forced downshift in an automotive automatic power transmission, which kickdown unit comprises a valve body, a valve chamber formed in the valve body, a valve spool slidably disposed in the valve chamber and having a relatively large valve land and a relatively small valve land biasing means for urging the valve spool in one direction, inlet and outlet ports communicating with the valve chamber, a control pressure port communicating with the valve chamber at a position to cause the control pressure therein to continuously act on the relatively large valve land for thereby urging the valve spool in another direction, a drain port communicating with said valve chamber and the degree of communication therebetween being controlled by said relatively large valve land and a nozzle leading from the valve chamber, said nozzle being opened and closed for controlling the control pressure acting on the relatively large valve land.

United States Patent 1 Enomoto Nov. 27, 1973 KICKDOWN UNIT FOR ANAUTOMOTIVE AUTOMATIC POWER TRANSMISSION [75} Inventor: KojiEnomoto,Yokohama,

' Japan [73] Assingee: Nissan Motor Company Limited,

7 Kanagawa-Ku, Yokohama, Japan 22 Filed: Dec. 14,1971

21 Appl. No.: 207,759

3,546,974 12/1970 Fox et al 74/869 Primary ExaminerRobert G. NilsonAttorneyJohn Lezdey [5 7 ABSTRACT A kickdown unit for effecting a forceddownshift in an automotive automatic power transmission, which kickdownunit comprises a valve body, a valve chamber formed in the valve body, avalve spool slidably disposed in the valve chamber and having arelatively large valve land and a relatively small valve land biasingmeans for urging the valve spool in one direction, inlet and outletports communicating with the valve chamber, a control pressure portcommunicating with the valve chamber at a position to cause the controlpressure therein to continuously act on the relatively large valve landfor thereby urging the valve spool in another direction, a drain portcommunicating with said valve chamber and the degree of communicationtherebetween being controlled by said relatively large valve land and anozzle leading from the valve chamber, said nozzle being opened andclosed for controlling the control pressure acting on the relativelylarge valve land.

12 Claims, 6 Drawing Figures PATENTEDHHVQ'I ms SHEET 10F 3 mwimmwma Q DE ISnFDO ROTATIONAL SPEED OF OUTPUT SHAFT INVENTOR E om 7'0 ATTORN YKICKDOWN UNIT FOR AN AUTOMOTIVE AUTOMATIC POWER TRANSMISSION Thisinvention relates to an automotive automatic power transmission and,more particularly, to a kickdown unit adapted to effect a forceddownshift during kickdown operation in the power transmission.

As is well known in the art, an automatic power transmission used in amotor vehicle commonly includes a hydraulic control system which isarranged to produce a shift pattern for selectively effecting a desiredgear ratio in accordance with variations in vehicle speed and engineload. To detect vehicle speed, a fluid pressure governor valve isutilized which produces a fluid pressure increasing upon an increase invehicle speed. This fluid pressure will be hereinafter referred to as agovernor pressure. The engine load is detected a modulating valve whichresponds to variations in intake manifild vacuum of an engine or theposition of an accelerator pedal to modulate a line pressure suppliedfrom an engine driven oil pump. This modulated line pressure will behereinafter called a throttle pressure. The governor pressure and thethrottle pressure thus obtained are utilized in the hydraulic controlsystem forcontrolling shift valves to selectively actuate plurality offriction elements for thereby providing the desired gear ratio.

A kickdown valve has been conventionally provided in the hydrauliccontrol system for effecting a forced downshift in the powertransmission to permit rapid acceleration under certain circumstances.In this prior practice, it is common practice to employ a solenoid whichis usually arranged to actuate a valve spool over its entire travelagainst the force of counteracting spring means. In such cases, thevalve spool must be precisely guided and the spring relatively powerful,resulting in relatively large capacity and high electric powerconsumption. Furthermore, the conventional kickdown valve is soconstructed as to selectively supply the line pressure to the associatedshift valve for biasing the same in a direction opposite to the governorpressure exerted thereon. Consequently, it is required that the shiftvalve associated with such kickdown valve be formed with an additionalvalve land on which the line pressure acts resulting in complicatedconstruction.

The principal object of the present invention is to provide an improvedkickdown unit which overcomes the drawbacks referred to and which isspecifically suited for use in an automotive automatic powertransmission.

In the accompanying drawings:

FIG. 1 is a sectional view of the kickdown unit according to the presentinvention;

FIG. 2 is a graph illustrating the characteristic of the kickdown unitof FIG. 1;

FIG. 3 is a sectional view showing a modified form of the kickdown unitshown in FIG. 1;

FIG. 4 is a sectional view of another modified form of the kickdown unitshown in FIG. 1;

FIG. 5 is a sectional view of still another modified form the kickdownunit shown in FIG. 1; and

FIG. 6 is a graph illustrating the characteristic of the kickdown unitshown in FIG. 5.

Referring now to FIG. 1, there is shown in section a kickdown unitaccording to the present invention, which is generally indicated byreference numeral 10. The kickdown unit 10 includes a valve body 11having therein a valve chamber 12, in which a valve spool 13 is slidablydisposed. The valve spool 13 is formed with a relatively small valveland 14 and a relatively large valve land 15. A biasing means 16 isprovided for biasing the valve spool 13 downwardly of the drawing. Inthe illustrated embodiment, the biasing means 16 is shown as a spring,which is associated with the small valve land 14.

An inlet port 17 is formed in the valve body 11 and communicates with afluid pressure supply passage 18, which in turn communicates with afluid pressure governor valve (now shown) of the hydraulic controlsystem in the power transmission so that a governor pressure whichvaries in proportion to the vehicle speed is supplied to the inlet port17. In the illustrated embodiment of FIG. 1, the inlet port 17communicates with the valve chamber 12 at a position between the valvelands l4 and 15.

The valve body 11 has formed therein an outlet port 19 whichcommunicates with the valve chamber 12. The outlet port 19 communicateswith a discharge passage 20, which in turn communicates with a shiftvalve (now shown) of the hydraulic control system in the powertransmission. The communication between the inlet and outlet ports 17and 19 is controlled by the valve land 15 of the valve spool 13. Thefluid pressure delivered to the valve chamber 12 between the valve lands14 and 15 acts on the differential area therebetween for biasing thevalve spool 13 downwardly of the drawing with the force of the spring16.

The bias the valve spool 13 upwardly as viewed in FIG. 1, a controlpressure port 21 is provided which introduces an output pressureappearing at the outlet port 19 into the valve chamber 12 as a controlpressure. The control pressure admitted to the valve chamber 12 acts onthe valve land 15 to bias the valve spool 13 upwardly against thecounteracting forces. In FIG. 1, the control pressure port 21 is shownas connected to the outlet port 19 through a branch passage 22, so thatthe output pressure at the outlet port 19 is introduced as the controlpressure to the control pressure port 21. The control pressure port 21may be provided therein a orifice 23 which restricts the rate of fluidflow therethrough.

A drain port 24 communicates with the valve chamber 12 and the degree ofcommunication therebetween is controlled by the valve land 15 of thevalve spool 13 so that the output pressure appearing at the outlet port19 is varied.

A nozzle 25 leads from the valve chamber 12 and is associated with theorifice 23 to vary the output pressure acting on the large valve land 15thereby to control the movement of the valve spool 13.

To open and close the nozzle 25, an actuator 26 is provided which has aplunger 27 adapted to selectively protrude and retract in accordancewith an electric signal applied thereto. The plunger 27 is positionedopposite to the nozzle 25 and is associated therewith for therebycontrolling the control pressure acting on the valve land 15, aspreviously noted. The actuator 26 may be of a solenoid or of any othersuitable construction.

Indicated at 28 is a drain port 28, through which an excessive fluid isdrained off.

When, the operation, the actuator 26 is deenergized, then the plunger 27retracts so that the nozzle 25 is opened. With the nozzle 25 beingopened, the control pressure prevailing in the valve chamber 12 isreleased through the nozzle 25 resulting in a drop in the controlpressure acting on the valve land 15. This causes the opposing forcesacting on the valve spool 13 to overcome the force developed by thecontrol pressure. Accordingly, the valve spool 13 is moved downwardly ofthe drawing, so that the drain port 24 is closed by the valve land 15whereas the outlet port 19 is brought into communication with the inletport 17. Thus, the governor-pressure delivered to the inlet port 17 isallowed into the outlet port 19 and, therefore, the governor pressure orthe output fluid pressure appearing at the outlet port 19 varies in amanner as shown by a curve a (FIG. 2).

When, in contrast, the actuator 26 is energized, the plunger 27 iscaused to protrude thereby closing the nozzle 25. Then, the controlpressure acting on the valve land 15 increases so that the magnitudethereof will be sufficient to urge the valve spool 13 upwardly againstthe opposing force acting upon the differential area between the valvelands 14 and 15 and the force of the spring 16. In this condition, thedrain port 24 is opened by the valve land 15 and, accordingly, thecontrol pressure in the valve chamber 12 is released resulting in adecrease in the control pressure. When this occurs, the valve spool 13is moved again downwardly by the opposing forces exerted thereon. Underthese conditions, the valve spool 13 is situated in a position where theforce developed by the control pressure balances with the opposingforces.

Now assuming that the valve spool 13 is positioned in balancedcondition, then the following equation will be obtained:

1 2) u AIPQI "f and, therefore,

wherein A, and A are effective sectional areas of valve lands 15 and 14,f the spring force, F, the governor pressure at the inlet port 17 and Pthe output fluid pressure at the outlet port 19. Thus, it will beunderstood that the output fluid pressure varies in such a manner asshown by a curve b in FIG. 2.

A modification of the kickdown unit of FIG. 1 is illustrated in FIG. 3,wherein like component parts are designated by the same numerals. Thismodified form of the kickdown unit 10 is similar to that of FIG. 1except that the inlet port 17 is provided in a position to cause thegovernor pressure to be applied on the upper side of the valve land 14,that the degree of communication between the inlet and outlet ports 17and 19 is controlled by the relatively small valve land 14, that thedrain port 28 communicates with the valve chamber 12 between the valvelands 14 and 15, and that the spring 18 is disposed between the valveland and a shoulder portion 11a of the valve body 11. The operation ofthis modification is the same with that of first embodiment and,therefore, the descripting of the same is herein omitted for the sake ofsimplicity of description.

Another modified form of the kickdown unit accord ing to the presentinvention is illustrated in FIG. 4. In this modification, the kickdownunit 10 is further provided with an auxiliary inlet port 29 which isformed in the valve body 11. The auxiliary inlet port 29 communicateswith the valve chamber 12 at a position to be opened and closed by anauxiliary valve land 30. The auxiliary valve land 30 is formed on thevalve spool 13 and has the same diameter in section with the valve land15. An auxiliary outlet port 31 is also formed in the valve body 11 andcommunicates with the valve chamber 12. The auxiliary outlet port 31communicates with the outlet port 19 with which the control pressureport 21 also communicates through the branch passage 22. In thisillustrated embodiment, the nozzle 25 leads through the drain port 24from the valve chamber 12 and the orifice 23 is dispensed with.

When, in operation, the actuator 26 is energized, the plunger 27 iscaused to retract thereby opening the nozzle 25. The control pressuredistributed to the drain port 24 is then drained off through the nozzle25 to decrease the control pressure acting on the valve land 15.Consequently, the valve spool 13 is moved downwardly of the drawing bythe force acting on the differential area between the valve lands 14 and30 and the force of the spring 16. This causes the outlet port 19 tocommunicate with the inlet port 17, to which the governor pressure isdistributed. The governor pressure distributed to the outlet port 19 isthen delivered through the branch passage 22 to the auxiliary outletport 31 and the control pressure port 21. The governor pressure in thecontrol pressure port 21 is introduced to the valve chamber 12 as thecontrol pressure, which acts on the valve land 15. If, in this instance,the drain port 24 is closed by the valve land 15, the force developed bythe control pressure in the valve chamber 12 is sufficient to urge thevalve spool 13 upwardly against the opposing forces acting thereon.Accordingly, the drain port 24 is opened again by the valve land 15.Under these conditions, the valve spool 13 is situated in the valvechamber 12 in a position where the forces acting on the valve spool 13balance with each other. Thus, the output fluid pressure appearing atthe outlet port 19 or discharge passage 20 varies in a manner as shownby the curve b in FIG. 2.

When, in contrast, the actuator 26 is de-energized, the plunger 27protrudes so that the nozzle 25 is closed. With the nozzle 25 beingclosed, the control pressure prevailing in the valve chamber 12increases thereby moving the valve spool 13 upwardly against theopposing forces. Consequently, the auxiliary outlet port-31 is broughtinto communication with the auxiliary inlet port 29 and, therefore, thegovernor pressure therein is passed through the branch passage 22 to thefluid pressure discharge passage 20. In this condition, the governorpressure available to the passage 20 varies in a manner as shown by thecurve a in FIG. 2.

FIG. 5 illustrates still another modified form of the kickdown unitaccording to the present invention. In this modified form, the shiftvalve 10 further includes an additional inlet port 33, which isselectively brought into communication with the outlet port 19 by therelatively small valve land 14. The communication between the inlet andoutlet ports 17 and 19 is selectively established by the relativelylarge valveland 15. The additional inlet port 33 communicates with aline pressure supply passage 34 which may be connected to a source ofline pressure. In FIG. 5, the control pressure port 21 is shown ascommunicating with the governor pressure supply passage 18 whichcommunicates with the inlet port 17.

When, in operation, the actuator 26 is energized, the plunger 27retracts so that the nozzle 25 is opened. In this condition, the controlpressure in the valve chamher 12 is released through the nozzle 25,while the governor pressure in the passage 18 is distributed as thecontrol pressure to the control pressure port 21 through the orifice 23.Accordingly, the control pressure decreases below the governor pressureprevailing in the passage 18. This causes the valve spool 13 to moveupwardly of the drawing by the force acting on the differential areabetween the valve lands l4 and 15 and the force of the spring 16. Whenthis occurs, the outlet port 19 is brought into communication with theinlet port 17, from which the-governor pressure is admitted to the fluidpressure discharge 20. It is to be noted that the valve spool 13 ismaintained in the upward position when the following relation exists:

where A and A indicate the effective sectional areas of valve lands 15and 14, P the control pressure acting on the relatively large valve land15 and P the governor pressure prevailing in the passage 18. It will beappreciated that the output fluid pressure available to the passage 20varies in a manner as shown by a curve c in FIG. 6 during kickdownoperation.

When, in contrast, the actuator 26 is deenergized, then the plunger 27is caused to protrude so that the nozzle is closed. As the nozzle 25 isclosed by the plunger 27 of the actuator 26, the control pressure actingon, the relatively large valve land 15 will be equal in level to thegovernor pressure in the passage 18. As previously noted, the governorpressure increases in proportion to the rotational speed of the outputshaft of the power transmission, so that the valve spool 13 will bemoved downwardly against the force acting on the differential areabetween the valve lands l4 and 15 and the force of the spring 16. Theforce biasing the valve spool 13 downwardly as viewed in FIG. 5 isexpressed by A X P (A X P while the force biasing the valve spool 13upwardly of the drawing is expressed by (A A )P where P indicates thepressure acting on the differential area between the valve lands 14 and15. As discussed above, if the governor pressure increases, then thevalve spool 13 is moved downwardly so that the additional inlet port 33is caused to communicate with the valve chamber 12 by the valve land 14whereas the inlet port 17 is prevented from communication with the valvechamber 12. Consequently, the line pressure in the passage 34 isadmitted to the valve chamber 12 thereby increasing the pressure P,therein. As a result, the force acting on the differential area betweenthe valve lands 14 and 15 and the force of the spring 16 overcome theopposing force acting on the valve land 15. This causes the valve spool13 to move upwardly of the drawing. Under these conditions, the valvespool 13 will be situated in a position where the counteracting forcesbalance with each other. This balanced condition is expressed by thefollowing equation:

l u r 2) 'f It will thus be seen that the pressure P, will vary in amanner as shown by a curve d in FIG. 6.

It will now be appreciated that the actuator of the kickdown unitimplementing the present invention is so arranged as to need a shorttravel of a few tenths of a millimeter while the actuator will have onlyvery low power consumption.

It will further be understood that the kickdown unit according to thisinvention is simple in construction and economical to manufacture.

It will also be noted that the kickdown unit embodying the presentinvention is arranged to provide a lower fluid pressure to theassociated shift valve during kickdown operation whereby a shiftingpoint will be varied to a higher vehicle speed side.

What is claimed is:

l. A kickdown unit for an automotive automatic power transmission,comprising a valve body, a valve chamber formed in said valve body, avalve spool slidably disposed in said valve chamber and having arelatively large valve land and relatively small valve land, biasingmeans for biasing said valve spool in one direction, an inlet portformed in said valve body and communicating with said valve chamber, anoutlet port formed in said valve body and communicating with said valvechamber, a control pressure port communicating with said valve chamberat a position to cause a control pressure therein to continuously act onsaid large valve land for thereby biasing said valve spool in anotherdirection against the force of said biasing means, a drain portcommunicating with said valve chamber and the degree of communicationtherebetween being controlled by said relatively large valve land forthereby varying an output pressure appearing at said outlet port, and anozzle leading from said valve chamber, said nozzle being opened andclosed for controlling said control pressure acting on said largevalveland.

2. A kickdown unit according to claim 1, further comprising an actuatorhaving a plunger associated with said nozzle to vary said controlpressure exerted on said large valve land.

3. A kickdown unit according to claim 2, wherein said biasing means is aspring.

4. A kickdown unit according to claim 3, wherein said control pressureport communicates with said outlet port.

5. A kickdown unit according to claim 1, further comprising an auxiliaryinlet port communicating with said inlet port and an auxiliary outletport communicating with said outlet port, and wherein said valve spoolfurther includes an auxiliary valve land between said small and largevalve lands to control fluid communication between said auxiliary inletand outlet ports.

6. A kickdown unit according to claim 5, wherein said control pressureport communicates with said auxiliary outlet port communicating withsaid outlet port.

7. A kickdown unit according to claim 5, wherein said biasing means is aspring.

8. A kickdown unit according to claim 7, further comprising an actuatorhaving a plunger associated with said nozzle to open and close saidnozzle.

9. A kickdown unit according to claim 8, wherein said nozzle leads fromsaid valve chamber through said drain port.

10. A kickdown unit according to claim 1, further comprising anadditional inlet port, said small valve land controlling fluidcommunication between said additional inlet port and outlet port whereassaid large valve land controls fluid communication between said inletand outlet ports.

11. A kickdown unit according to claim 10, further comprising anactuator having a plunger associated with said nozzle to open and closesaid nozzle.

12. A kickdown unit according to claim 11, wherein said inlet portcommunicated with said control pressure port.

1. A kickdown unit for an automotive automatic power transmission,comprising a valve body, a valve chamber formed in said valve body, avalve spool slidably disposed in said valve chamber and having arelatively large valve land and relatively small valve land, biasingmeans for biasing said valve spool in one direction, an inlet portformed in said valve body and communicating with said valve chamber, anoutlet port formed in said valve body and communicating with said valvechamber, a control pressure port communicating with said valve chamberat a position to cause a control pressure therein to continuously act onsaid large valve land for thereby biasing said valve spool in aNotherdirection against the force of said biasing means, a drain portcommunicating with said valve chamber and the degree of communicationtherebetween being controlled by said relatively large valve land forthereby varying an output pressure appearing at said outlet port, and anozzle leading from said valve chamber, said nozzle being opened andclosed for controlling said control pressure acting on said largevalveland.
 2. A kickdown unit according to claim 1, further comprisingan actuator having a plunger associated with said nozzle to vary saidcontrol pressure exerted on said large valve land.
 3. A kickdown unitaccording to claim 2, wherein said biasing means is a spring.
 4. Akickdown unit according to claim 3, wherein said control pressure portcommunicates with said outlet port.
 5. A kickdown unit according toclaim 1, further comprising an auxiliary inlet port communicating withsaid inlet port and an auxiliary outlet port communicating with saidoutlet port, and wherein said valve spool further includes an auxiliaryvalve land between said small and large valve lands to control fluidcommunication between said auxiliary inlet and outlet ports.
 6. Akickdown unit according to claim 5, wherein said control pressure portcommunicates with said auxiliary outlet port communicating with saidoutlet port.
 7. A kickdown unit according to claim 5, wherein saidbiasing means is a spring.
 8. A kickdown unit according to claim 7,further comprising an actuator having a plunger associated with saidnozzle to open and close said nozzle.
 9. A kickdown unit according toclaim 8, wherein said nozzle leads from said valve chamber through saiddrain port.
 10. A kickdown unit according to claim 1, further comprisingan additional inlet port, said small valve land controlling fluidcommunication between said additional inlet port and outlet port whereassaid large valve land controls fluid communication between said inletand outlet ports.
 11. A kickdown unit according to claim 10, furthercomprising an actuator having a plunger associated with said nozzle toopen and close said nozzle.
 12. A kickdown unit according to claim 11,wherein said inlet port communicated with said control pressure port.